The present invention relates to a fuel-injection system for an automotive fuel-injected engine that fuel is injected into a combustion chamber via a fuel injector.
Generally, there are two types of electronic fuel-injection systems mounted on automotive vehicles, namely a so-called non-return system (see FIG. 7) and a so-called full-return system (see FIG. 8). The non-return system shown in FIG. 7 includes at least a fuel tank 1, a fuel pump 3, a fuel supply line 5, fuel injectors 10, an upstream pressure regulator 11, and a fuel return line 12. For instance, in a four-wheeled vehicle, tank 1 is usually mounted at the rear of the vehicle and has a fuel storage capacity of several tens of liters. Tank 1 is constructed as a sealed fuel tank. Pump 3 is provided in the interior or exterior space of tank 1. Pump 3 is generally comprised of an electric fuel pump that is driven by an electric motor. Pump 3 is provided for inducting fuel 2 stored in tank 1 and for discharging pressurized fuel toward the upstream side of supply line 5. The non-return system of FIG. 7 is exemplified in a four-cylinder fuel-injected engine that has four fuel injectors 10 on each cylinder of an internal combustion engine 4 to deliver fuel 2 to each of four combustion chambers. Supply line 5 is provided for supplying fuel 2 to the respective injectors. Supply line 5 includes a feed pipe 6 extending from the front end of the vehicle to the rear end, fuel distributor pipes 7 and 8, and a connecting pipe 9 intercommunicating two distributor pipes 7 and 8. Feed pipe 6 is connected to the discharge outlet of pump 3 to supply fuel 2 to the respective fuel distributor pipes 7 and 8. Distributor pipes 7 and 8 are made of a metal pipe material having a substantially cylindrical shape and located near the combustion chambers so that distributor pipes 7 and 8 extend straight along the respective sidewall surfaces of engine 4. In the non-return system of FIG. 7, the pressurized fuel from pump 3 is discharged into the upstream side of feed pipe 6 and delivered into upstream pressure regulator 11 that prevents excessive pressure from developing and regulates the output pressure from upstream pressure regulator 11 to a predetermined pressure, for example, a pressure level ranging from 250 to 350 kPa. First, the fuel regulated by upstream pressure regulator 11 is supplied into the first distributor pipe 7 of distributor pipes 7 and 8. Then, the regulated fuel is further delivered via connecting pipe 9 to the second distributor pipe 8. The downstream end 8A of second distributor pipe 8 is formed as a dead end of supply line 5. As shown in FIG. 7, a first group of injectors 10, 10 are integrally connected to first distributor pipe 7, whereas a second group of injectors 10, 10 are integrally connected to second distributor pipe 8. In the system shown in FIG. 7, the four fuel injectors and distributor pipes 7 and 8 construct a so-called xe2x80x9cgallery-typexe2x80x9d fuel-pipe integrated fuel injection unit. An electromagnetic actuator (electromagnetic solenoid) is built within the injector body and is responsive to a control signal from an electronic engine control unit (ECU) to control both opening and closing of each fuel injector 10. When the actuator is energized and thus the injector valve of each fuel injector 10 opens, the fuel within distributor pipes 7 and 8 is sprayed or injected into the combustion chamber. The amount of fuel injected is controlled by a fuel-injection signal from the ECU. Generally, a pulsewidth modulated control signal or a duty-cycle modulated pulsewidth signal is used as the fuel-injection signal. Upstream pressure regulator 11 is disposed in a middle of feed pipe 6 of supply line 5 and includes an inflow conduit portion 11A, an outflow conduit portion 11B, and a return conduit portion 11C. Return conduit portion 11C is connected to return line 12 that is connected to tank 1. Upstream pressure regulator 11 uses intake manifold pressure (manifold vacuum) as a control pressure. Surplus fuel is returned through return line 12 to tank 1, after pressure-regulating action of upstream pressure regulator 11. As clearly seen in FIG. 7, an installation position of upstream pressure regulator 11 is spaced apart from engine 4. For instance, upstream pressure regulator 11 is mounted on a floor panel corresponding to the bottom portion of the engine room in order to suppress heat from being transferred from engine 4 to return line 12. Although it is not shown in FIG. 7, a fuel filter is disposed in feed pipe 6 and located between the discharge port of pump 3 and the pressure-regulator inflow conduit portion 11A to remove any impurities from the fuel flowing through feed pipe 6. According to the non-return system shown in FIG. 7, when pump 3 is activated and thus fuel 2 stored in tank 1 is discharged into feed pipe 6 of supply line 5, a portion of fuel discharged from pump 3 flows from the pressure-regulator inflow conduit portion 11A to the pressure-regulator outflow conduit portion 11B (see the fuel flow indicated by the arrow A) and is delivered into distributor pipes 7 and 8 located downstream of the pressure-regulator outflow conduit portion 11B. In this manner, a portion of fuel flowing through distributor pipes 7 and 8 and having the fuel-injection pressure controlled by upstream pressure regulator 11 can be injected through each fuel injector 10 into the combustion chamber. As indicated by the arrow B in FIG. 7, as a result of fuel-pressure regulating action of upstream pressure regulator 11, as the surplus fuel, most of the fuel discharged from pump 3 returns through the pressure-regulator return conduit portion 11C via return line 12 to tank 1, without flowing through distributor pipes 7 and 8.
On the other hand, in the full-return system shown in FIG. 8, one end of a fuel return line 13 is connected to the downstream end 8A of supply line 5, whereas the other end of return line 13 is connected to tank 1. A downstream pressure regulator 14 is disposed in a middle of return line 13. As seen in FIG. 8, downstream pressure regulator 14 includes an inflow conduit portion 14A that is connected to the downstream end 8A of second distributor pipe 8 via the upstream portion of return line 13, and a return conduit portion 14B that is connected to tank 1 via the downstream portion of return line 13. Downstream pressure regulator 14 functions to return the surplus fuel through the pressure-regulator return conduit portion 14B to tank 1 (see the return flow indicated by the arrow C in FIG. 8), while regulating the fuel passing through distributor pipes 7 and 8 and returning into return line 13 to the predetermined pressure level (250-350 kPa). According to the full-return system shown in FIG. 8, when pump 3 is activated and thus fuel 2 stored in tank 1 is discharged into feed pipe 6 of supply line 5, all the fuel discharged from pump 3 is delivered into first distributor pipe 7 (see the fuel flow indicated by the arrow A in FIG. 8). In this manner, a portion of fuel flowing through distributor pipes 7 and 8 and having the fuel-injection pressure controlled by downstream pressure regulator 14 can be injected through each fuel injector 10 into the combustion chamber. As indicated by the arrow C in FIG. 8, as a result of fuel-pressure regulating action of downstream pressure regulator 14, as the surplus fuel, most of the fuel discharged from pump 3 passes through distributor pipes 7 and 8 and thereafter consecutively returns via the pressure-regulator return conduit portion 14B and return line 13 to tank 1. In case of the full-return system of FIG. 8, the surplus fuel has to pass through distributor pipes 7 and 8. Heat is undesirably transferred from engine 4 to the surplus fuel passing through distributor pipes 7 and 8. That is, the high-temperature surplus fuel returns through downstream pressure regulator 14 and return line 13 to tank 1. Under a particular condition that a residual quantity of fuel in tank 1 is very little, a temperature in the fuel stored in tank 1 tends to rise owing to the high-temperature surplus fuel. The temperature rise causes the fuel to expand and to vaporize more readily, and thus the amount of generation of fuel vapor (evaporation gas) created in tank 1 tends to increase. This results in unstable fuel-injection amount control.
The non-return system of FIG. 7 has the following drawback. The downstream end 8A of second distributor pipe 8 is formed as a dead end of supply line 5, and therefore fuel vapor tends to be created within distributor pipes 7 and 8. There is a possibility that the fuel vapor prevailing in distributor pies 7 and 8 is injected from the injector valve together with fuel delivered into the fuel injector. As a result of this, an air/fuel mixture ratio (A/F) tends to change to an undesirably leaner mixture ratio. In particular, when restarting the engine under a condition wherein the engine has already been warmed up, during engine hot restart, there is an increased tendency for a restartability of the engine to be lowered owing to fuel vapors created within distributor pipes 7 and 8.
On the other hand, the full-return system of FIG. 8 has the following merit and demerit. The surplus fuel consecutively returns through the pressure-regulator return conduit portion 14B and return line 13 to tank 1 and therefore fuel vapors created within distributor pipes 7 and 8 can be carried into tank 1 together with the fuel flow from second distributor pipe via downstream pressure regulator 14 to tank 1. However, in the full-return system of FIG. 8, there is a problem of fuel vapors created owing to a temperature rise in the surplus fuel flowing through distributor pipes 7 and 8.
Accordingly, it is an object of the invention to provide a fuel-injection system, which is capable of enhancing an engine restartability by way of reduced fuel vapors and ensuring stable fuel-injection amount control by way of reduced evaporation gases created in a fuel tank.
In order to accomplish the aforementioned and other objects of the present invention, a fuel-injection system comprises a fuel tank storing fuel, a fuel injector injecting the fuel, a fuel pump inducting the fuel from the fuel tank and discharging pressurized fuel into a fuel supply line that is connected one end to the fuel pump and connected at the other end to the fuel injector, a pressure regulator disposed in a middle of the fuel supply line and located upstream of the fuel injector for regulating a pressure of the fuel flowing through the fuel supply line and for returning surplus fuel via the pressure regulator into the fuel tank, a reflux pipe arrangement that is located downstream of the fuel injector and connected at one end to a downstream end of the fuel supply line and connected at the other end to the fuel tank, and a reflux control device disposed in a middle of the reflux pipe arrangement for controlling a flow rate of the fuel flowing through the reflux pipe arrangement.
According to another aspect of the invention, a fuel-injection system comprises a fuel tank storing fuel, a fuel injector injecting the fuel, a fuel pump inducting the fuel from the fuel tank and discharging pressurized fuel into a fuel supply line that is connected one end to the fuel pump and connected at the other end to the fuel injector, a pressure regulator disposed in a middle of the fuel supply line and located upstream of the fuel injector for regulating a pressure of the fuel flowing through the fuel supply line and for returning surplus fuel via the pressure regulator into the fuel tank, a reflux pipe arrangement that is located downstream of the fuel injector and connected at one end to a downstream end of the fuel supply line, the other end of the reflux pipe arrangement extending toward the fuel tank, and a reflux control valve disposed in a middle of the reflux pipe arrangement for selectively establishing and blocking fluid communication between the reflux pipe arrangement and the fuel tank.
According to a further aspect of the invention, a fuel-injection system comprises a fuel tank storing fuel, a fuel injector injecting the fuel, a fuel pump inducting the fuel from the fuel tank and discharging pressurized fuel into a fuel supply line that is connected one end to the fuel pump and connected at the other end to the fuel injector, a pressure regulator disposed in a middle of the fuel supply line and located upstream of the fuel injector for regulating a pressure of the fuel flowing through the fuel supply line and for returning surplus fuel via the pressure regulator into the fuel tank, a reflux pipe arrangement that is located downstream of the fuel injector and connected at one end to a downstream end of the fuel supply line, the other end of the reflux pipe arrangement extending toward the fuel tank, and an orifice member constructed integral with the pressure regulator and disposed in a middle of the reflux pipe arrangement for restricting a flow rate of the fuel flowing through the reflux pipe arrangement.
According to a still further aspect of the invention, a fuel-injection system for an internal combustion engine comprises a sealed fuel tank storing fuel, a fuel injector injecting the fuel, a fuel pump inducting the fuel from the fuel tank and discharging pressurized fuel into a fuel supply line that is connected one end to the fuel pump and connected at the other end to the fuel injector, the fuel supply line comprising a distributor pipe located near combustion chambers of the engine and a feed pipe extending from the fuel pump to distributor pipe, a pressure regulator disposed in a middle of the feed pipe and located upstream of the fuel injector for regulating a pressure of the fuel flowing through the fuel supply line and for returning surplus fuel via the pressure regulator into the fuel tank without flowing through the distributor pipe, a reflux pipe arrangement that is located downstream of the fuel injector and connected at one end to a downstream end of the distributor pipe and connected at the other end to the fuel tank, and a reflux control device disposed in a middle of the reflux pipe arrangement for controlling a flow rate of the fuel flowing through the reflux pipe arrangement.
According to another aspect of the invention, a fuel-injection system for an internal combustion engine comprises a sealed fuel tank storing fuel, a fuel injector injecting the fuel, a fuel pump inducting the fuel from the fuel tank and discharging pressurized fuel into a fuel supply line that is connected one end to the fuel pump and connected at the other end to the fuel injector, the fuel supply line comprising a distributor pipe located near combustion chambers of the engine and a feed pipe extending from the fuel pump to distributor pipe, a pressure regulator disposed in a middle of the feed pipe and located upstream of the fuel injector for regulating a pressure of the fuel flowing through the fuel supply line and for returning surplus fuel via the pressure regulator into the fuel tank without flowing through the distributor pipe, a reflux pipe arrangement that is located downstream of the fuel injector and connected at one end to a downstream end of the distributor pipe and connected at the other end to the fuel tank, and a reflux control valve disposed in a middle of the reflux pipe arrangement for selectively establishing and blocking fluid communication between the reflux pipe arrangement and the fuel tank.
According to another aspect of the invention, a fuel-injection system for an internal combustion engine comprises a sealed fuel tank storing fuel, a fuel injector injecting the fuel, a fuel pump inducting the fuel from the fuel tank and discharging pressurized fuel into a fuel supply line that is connected one end to the fuel pump and connected at the other end to the fuel injector, the fuel supply line comprising a distributor pipe located near combustion chambers of the engine and a feed pipe extending from the fuel pump to distributor pipe, a pressure regulator disposed in a middle of the feed pipe and located upstream of the fuel injector for regulating a pressure of the fuel flowing through the fuel supply line and for returning surplus fuel via the pressure regulator into the fuel tank without flowing through the distributor pipe, a reflux pipe arrangement that is located downstream of the fuel injector and connected at one end to a downstream end of the distributor pipe and connected at the other end to the fuel tank, and an orifice member constructed integral with the pressure regulator and disposed in a middle of the reflux pipe arrangement for restricting a flow rate of the fuel flowing through the reflux pipe arrangement.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.